The field of the present invention relates to compound archery bows. In particular, compound archery bows are disclosed herein that include a pulley-and-cable mechanism for applying tension to a power cable of the bow.
For purposes of the present disclosure and appended claims, the terms “compound archery bow” or “compound bow” shall denote an archery bow that uses a levering system, usually comprising one or more cables and pulleys, to bend the limbs as the bow is drawn. A wide variety of compound archery bows include one or two power cables. Conventionally, each power cable is connected at one end to one bow limb and is engaged at its other end to be taken up by a power cam of a pulley member rotatably mounted on the other bow limb. Tension developed as the bow is drawn and the power cable is taken up by the power cam causes deformation of the bow limbs and storage of potential energy therein. A portion of that potential energy is transformed into the kinetic energy of the arrow shot by the bow. Examples of compound bows include dual-cam bows, bows that employ a Binary Cam System®, hybrid-cam bows, or single-cam bows. A few examples of these various compound bow types are disclosed in the following patents, all of which are incorporated by reference as if fully set forth herein:    U.S. Pat. No. 4,686,955 entitled “Compound archery bows” issued Aug. 18, 1987 to Larson, disclosing an example of a dual-cam compound bow;    U.S. Pat. No. 7,305,979 entitled “Dual-cam archery bow with simultaneous power cable take-up and let-out” issued Dec. 11, 2007 to Yehle, disclosing an example of a compound bow that employs a Binary Cam System®;    U.S. Pat. No. 6,871,643 entitled “Eccentric elements for a compound archery bow” issued Mar. 29, 2005 to Cooper et al, disclosing an example of a hybrid-cam compound bow; and    U.S. Pat. No. 5,368,006 entitled “Dual-feed single-cam compound bow” issued Nov. 29, 1994 to McPherson, disclosing an example of a single-cam compound bow.
An example of a conventional dual-cam compound bow 10 is illustrated in FIGS. 1 and 2A-2B. FIG. 1 shows the entire bow in an undrawn state (i.e., at brace), and FIGS. 2A and 2B show details of the pulley members and cables at brace and at full draw, respectively. The bow 10 comprises a substantially rigid riser 15, first and second resilient bow limbs 11 and 12, respectively, first and second pulley members 20 and 30, respectively, draw cable 16, and first and second power cables 22 and 32, respectively. The first and second bow limbs 11 and 12 are attached to corresponding first and second end portions of the riser 15. The first pulley member 20 is rotatably connected to the first bow limb 11 at a corresponding pulley connection point and includes a draw cable journal (on the periphery of a draw cable cam 24) and a first power cam 26. The second pulley member 30 is rotatably connected to the second bow limb 12 at a corresponding pulley connection point and includes a draw cable journal (on the periphery of a draw cable cam 34) and a second power cam 36. The draw cable 16 is engaged with the respective draw cable journals of the draw cable cams 24 and 34. The draw cable 16 is arranged to rotate the first and second pulley members 20 and 30 as the bow 10 is drawn and the draw cable 16 is let out from the draw cable journals of cams 24 and 34. The first power cable 22 is engaged at its first end to be taken up by the first power cam 26 as the bow 10 is drawn and the first pulley member 20 rotates (FIG. 2B), and is connected at its second end to the second bow limb 12. The second power cable 32 engaged at its first end to be taken up by the second power cam 36 as the bow 10 is drawn and the second pulley member 30 rotates, and is connected at its second end to the first bow limb 11.
When bow 10 is drawn, the power cams 26 and 36 take up the respective power cables 22 and 32. The resulting tensioning of the power cables 26 and 36 deforms the bow limbs 11 and 12, thereby storing potential energy in the limbs. When the drawn bow is released to shoot an arrow, a portion of the stored potential energy is converted to kinetic energy of the arrow. The relative sizes, shapes, positions, or orientations of the draw cable cams 24/34 and the power cable cams 26/36 can be arranged in any suitable way to provide desired draw force characteristics of the dual-cam bow 10. The relative sizes, shapes, positions, and orientations shown in FIGS. 1 and 2A-2B are exemplary only.